This invention relates generally to an electrostatographic printer machine, and more particularly concerns a cleaning apparatus.
Blade cleaners have long been attractive because of their low cost, simplicity and ability to clean most contaminate materials from the photoreceptor. The major drawback to blade cleaners has been the randomness of their failures. The Weibull characteristics (where Weibull characteristics are the distribution of failure probabilities defined by the equation: EQU P(N)=(1-e).sup.-((N-N.spsb.o.sup.)/N.spsb.a.sup.).spsp.b
where P(N)=cumulative failure probability at life N, ##STR1## for the failure of a blade have been estimated as a characteristic life of 648Kc (Kc:K=1000 and c=copies or prints), and no minimum life (no life below which failures are not expected, i.e failures can occur from the start of use) and a slope of 1.2 (where a slope of 1 indicates random failure and a 3.57 slope indicates a normal distribution for determinable failure). These values yield a B.sub.5 life of 50 Kc and a B.sub.50 life of 458Kc. (B.sub.5 life is where 5% of total population of blades have failed and B.sub.50 life is where 50% of the total population of blades has failed.) These Weibull statistic values are for a single blade cleaning system. In low volume machines the blade cleaner has been the cleaner of choice because of it's low cost. The random failure mode has been tolerated because of the low monthly copy volume. Blades have been used in mid volume machines but the random failure mode has been troublesome. Since blade failure is random, no meaningful preventative replacement interval can be determined. High volume machines have not utilized cleaning blades as a viable option because of the random failure mode problem.
Several methods for sensing cleaning failures have been attempted. Some of these methods are based on an optical system which observes toner on the photoreceptor after the photoreceptor has been cleaned. Other methods include attempting to detect deterioration of the blade cleaning edge. And, at least one copier utilizes a diagnostic routine which generates a stress cleaning condition at the infrared densitometer (IRD) location and then looks at the photoreceptor, after cleaning, for a failure. (IRD is an optical device which measures infrared reflection from a toner patch on the photoreceptor. The amount of infrared absorbed or scattered indicates density of toner patch.) However, in each of the aforementioned methods, when a failure occurs, manual replacement (i.e. by a technical representative) of the cleaning blade is required. Many technical representatives also use their own stress test for blade cleaners. They look for streaks on the first white copy after dark dustings have been sent into the cleaner.
It has been found that the use of a preclean toner charging device can decrease the cleaning stress to a blade cleaner. For some types of toners, especially color toners, this preclean treatment may be necessary to obtain acceptable cleaning at reasonable blade loads.
The following disclosures may be relevant to various aspects of the present invention and may be briefly summarized as follows:
U.S. Pat. No. 5,081,505 to Ziegelmuller et al. discloses a rotatable wiper blade roller for cleaning residual toner particles from an image-bearing surface that includes a plurality of indexable wiper blades. The blades engage the image-bearing surface at an angle of 60.degree. to 85.degree. defined in the direction of particle removal by the cleaning edge of each such blade and image-bearing surface. The blades are cleaned secondarily by an intermittently rotatable fur brush that is completely out of contact with the image-bearing surface.
U.S. Pat. No. 4,967,238 to Bares et al. discloses an arrangement for detecting toner or debris deposits on an imaging surface arranged downstream from the cleaning station. The imaging surface is illuminated by a light source, a light intensity detecting sensor arrangement is provided to view the illuminated surface and produce a signal representative of detected light intensity, and a response signal is produced indicative of the condition of the imaging surface.